Lubricating oil compositions



United States Patent M Int. Cl. Cm 1/32 US. Cl. 25251.5 2 Claims ABSTRACT OF THE DISCLOSURE The invention is lubricant compositions containing certain substituted 2-hydroxyphenylamine compounds as antioxidants. The compositions also show surprising thermal stability.

This invention relates to lubricant compositions, in particular to lubricant compositions comprising an antioxidant and is a continuation in part of application Ser. No. 412,854, filed Nov. 20, 1964, and now abandoned US. Patent 3,149,933 describes the use of certain 2-hy droxyphenylamine compounds as stabilizers for liquid fuels. It is surprisingly found that some of these compounds, and also some other Z-hydroxyphenylamine compounds may be used as antioxidants in lubricants.

It is surprising that the 2-hydroxyphenylamines can be used in lubricants as the requirements for a stabilizer for use in liquid fuel and an antioxidant for use in lubricants are completely different. In a fuel, the stabilizer is merely added to the fuel and preserves it during storage. The fuel is then burned and the function of the stabilizer is completed. In a lubricant, the situation is considerably more complex and the requirements for the antioxidant are more demanding. A lubricant composition comprises a lubricant base, which may be a mineral hydrocarbon or a synthetic ester base, for example, together with many other additives, such as over-based additives, detergents, antifoam additives, dispersants, extreme pressure additives, viscosity index improvers, metal de-activators and anti-corrosion agents, depending on the function of the lubricant composition. The selection of the additives which go to form a useful composition is rendered diflicult as the additives and the base must be capable of being stored for a considerable time before use, and during use the composition may be subjected to high temperatures and pressures. Not only must there be no undesirable chemical reaction between the components during this time, but the presence of one additive must not have a deleterious effect on the properties of another. For example in extreme pressure lubricants it is usual to have antiseizure additive, to prevent metal to metal contact, and a seizure-recovery additive to control such wear as inevitably or even desirably takes place. However it is often found that addition of an antiseizure additive to a composition having good seizure recovery properties leads to a lowering of standard in both these properties. In addition, the properties of the products of the inevitable breakdown of the composition must be kept in mind when preparing a lubricant composition. The composition, having met all these requirements, is then subjected to stringent viscosity tests.

According to the present invention a lubricant composition comprises a lubricant base and, as an anti- 3,498,916 Patented Mar. 3, 1970 oxidant, at least one substituted Z-hydroxyphenylamine of formula in which X represents an aromatic radical selected from the group consisting of the phenyl radical, the naphthyl radical, the biphenyl radical and substituted phenyl radicals wherein the substituents are selected from the group of lower alkyl, lower alkoxy and halogen, or radicals of formula HO R1 YNH wherein Y is an arylene radical of up to 13 carbon atoms; and R and R represent radicals selected from the group consisting of alkyl, aralkyl, alkenyl and aralkenyl radicals of up to 9 carbon atoms.

R and R can be the same or different. The positions on the aromatic rings which are shown unsubstituted in the above formulae may, if desired, be occu pied by further substituents, such as alkyl groups or halogen atoms.

According to one aspect of the invention, the group Y is a para-phenylene group, a meta-tolylene group, a para-xylylene group, a group of formula or a group of formula In one preferred aspect of the invention, the group X is a of formula the compounds of formulae l e on no R 52 NH @011 NH 1' where R is tert-butyl.

The 2-hydroxyphenylamines with which the instant invention is concerned are also found to be stable in lubricating compositions at surprisingly high temperatur s. The 2-hydroxyphenylamine compounds, being substituted in the 3 and 5 positions, show the structure of hindered phenols. It is well know that in general hindered phenols are not stable at elevated temperatures and will show appreciable decomposition at about 200 C. The compounds used in the present invention are shown in the examples to be stable in lubricant compositions subjected to tests at 500 F. (250 C.).

The lubricant base can be, for example, a hydrocarbon oil of the type used in crankcase oil formulations for internal combustion engines. Alternatively the lubricant base can be a synthetic lubricant, for example an alkyl ester of an aliphatic dicarboxylic acid, such as dioctyl sebacate or a lubricant base of the type described in applicants US. Patent No. 3,313,732.

Lubricant compositions of the invention can additionally contain additives such as corrosion inhibitors, viscosity index improvers, pour point depressants, dispersants and detergents.

Some of the substituted 2-hydroxyphenylamines mentioned above are new compounds.

Accordingly, the present invention further provides substituted Z-hydroxyphenylamines of formula R (INC-I HO 1'21 with an aromatic amine of formula H NZ where Z is phenyl, naphthyl, biphenyl, or phenyl substituted with alkyl, alkoxy or halogen.

A general method of preparation of these compounds is to dissolve the 3,5-disubstituted catechol in light petroleum and add this solution to a solution of the aromatic amino compound in light petroleum. A few drops of a tertiary organic amine, for example trimethylamine may be added as catalyst, and the mixture allowed to stand for several hours. The product, a substituted 2-hydr0xyphenylamine, separates and can be removed by filtration or isolated by evaporation of the solvent, then washed with ligroin and dried.

The following examples illustrate the invention. EX- amples 1, 2 and 3 relate to the use as antioxidants of compounds having the formula:

R (I) H EXAMPLE 1 Compositions consisting of dinonyl sebacate with various antioxidants were tested for oxidative stability by the method of the American Standard for the Testing of Materials No. D97256, the test being carried out in glass apparatus at 500 F. The results are shown in Table l, in which similar results are included for dinonyl sebacate in the absence of a stabiliser.

TABLE 1 Weight 10s Appearance Antioxident percent after test A. Prior Art:

1. None 79 Very dark, heavy sludge 2. 0.5% phenothiazine 3. 0.5% 3:7-dioctylphenothiaziue and varnish.

D0. Darkened, slight varnish.

B. Substituted 2-hydroxy-pheny1amines:

4. 0.5% (R =R tertiary butyl; R =methyl). 5. 0.5% (R R tertiary hutyl; R =ch10r0) 6. 0.5% (R =R tertiary butyl; R =eth0xy) D 0. Darkened, some varnish.

wherein Y, R and R have the meanings ascribed thereto above.

The new compounds of the invention can be prepared by the condensation of a 3,5-disubstituted catechol of formula R OH with an aromatic amine of formula H NZ where Z R R and Y have the meanings ascribed thereto above. The other compounds useful in accordance with the Antioxidant present invention can be prepared by the condensation of a 3,5-disubstituted catechol of formula OH I IV These results clearly demonstrate the superior stability at 500 F. of lubricant compositions containing antioxidants of the present invention over those containing antioxidants of the prior art.

EXAMPLE 2 The results are given in Table 2.

TABLE 2 Weight loss, percent Appearance after test Very dark, semisolid. Darkened slight varnish.

These results again demonstrate the superiority at 500 F. of the antioxidant of the present invention over the antioxidant of the prior art.

EXAMPLE 3 A further series of compositions consisting of dioctyl sebacate, di-penta-erythritol tricaprylate tributyrate (PBQ), the octyl tetra-ester of cyclohexanone 2221626 tetrakis-(beta-propionic acid) (CHTP), and a mixture of 55 parts of the 2-ethylhexy1 tetra-ester of cyclohexanone 222:6:6-tetrakis (beta-propionic acid) with 45 parts of dinonyl sebacate, respectively, was tested in the manner disclosed in Example 1. The results are shown in Table 3.

TABLE 3 6 method of the American Standard for the Testing of Materials No. D972-56, the test being carried out in glass apparatus at 500 F. The results are shown in Table 5, in which similar results are included for dinonyl sebacate Synthetic Lubricant 2. Dipentaerythritol tricaprylate tributyrate (P.C.B.)

3. Octyl tetra-ester of C.H.T.P N

4. 55:45 mixture (as described above) Examples 4 and 5 relate to the use in lubricant compositions as antioxidants of compounds having the formula H OH HO R EXAMPLE 4 Compositions consisting of a lubricating oil base (containing detergent and alkaline additives) with various antioxidants were tested for corrosion and volatile acid production in a laboratory scale copper-lead bearing corrosion test. The results are shown in Table 4 which also includes similar results for the lubricating oil base in the absence of a stabiliser.

5 in the absence of a stabiliser.

Weight loss percent Antioxidant 500 F.

None i. 58 As in Exam 97 None 16 As in Example 1 (4)..-" 8 one As in Example 1 (4) 6 None 35 As in Example 1 (4) 26 TABLE 5 Wellght Antioxidant percgr it z Prior Art Substituted 2-hydroxyphenylaminez 0.5% (R =R =tert.butyl) 74 0.5% (R R =tert.butyl) 54. 4

0.5% (R R =tert.butyl) 54. 2

TABLE 4 Onset of Rate of Corrosion Volatile acids Coking Conc., corrosion, corrosion, after 18 in millimoles,. panel Antioxidant percent hours mg./hr. his, mgs. 100 g. rating Prior Art:

None 7 542 More than 35 2 Ethyl 702 0. 25 14 34 137 16. 1 1 Ethyl 736 0. 15 10 39 325 29. 9 Substituted 2-hydroxyphenylamine, R =R tert. butyl:

2. Y= 0. so 17. o 21 7. 9 3

The coking panel rating gives an indication of the forma- Examples 6 and 7 relates to the use in lubricant composition of insoluble polymeric materials which cause piston deposits. The panels are read in arbitrary units from 0 corresponding to as new through 7 corresponding to complete coking. In general ratings from 0-3 are satisfactory.

EXAMPLE 5 Compositions consisting of dinonyl sebacate with varitions as antioxidants of compounds having the formula:

Compositions consisting of a lubricating oil base with ous antioxidants were tested for oxidative stability by a various antioxidants were tested for oxidative stability and bearing corrosion in a standard Petter W.1 engine test. The results are shown in Table 6 in which similar results are included for the lubricating oil base in the absence of a stabiliser, and the standard pass level accepted for lubriwherein Y is an arylene radical of up to 13 carbon atoms; and

R and R represent radicals selected from the group consisting of alkyl, aralkyl, alkenyl and aralkenyl radicals of eating 011s. 5 up to 9 carbon atoms.

TABLE 6 Bearing wt. Piston Ratings loss (mg.)

after A Under Oil Antioxidant 36 hours Skirt crown ring Pass leveL. i. Less than 25 9-10 8. 5-10 9. 5-10 Prior Art:

None 1, 900 8. 8 9. 5 9. 8 0.25% Ethyl 702. 25. 0 9. 9 9.0 9. 8 0.15% Ethyl 736 20. l 9. 9 r 9. 0 9. 8 Substituted Z-h'ydroxy phenylamine, (R =tertiary butyl R =tertiary butyl X=p-tolyl) EXAMPLE 7 duction in a laboratory scale copper-lead bearing corrosion test. The results are shown in Table 7 in which similar results are included for the lubricating oil base in the absence of a stabiliser.

2. A lubricant composition according to claim 1 in which X is a radical of formula and Y is an arylene radical selected from the group con- TABLE 7 Onset of I Rate of Corrosion Volatile acids Coking Conc. corrosion, corrosion, after 18 in millimoles, panel Antioxidant percent hrs. mg./hr. hrs., rugs. 100 g. rating Prior Art:

7 50 542 More than 2 14 34 137 16. 1 1 Ethyl 731i 10 39 325 29. 9 2 Substituted Z-hydroxyphenylamine: A. R =tert. butyl; Rz=tert. butyl; X=p-tolyl 0. th M01r7e 60 8. 7 1

an E. R =R =tert. butyl:

C. R IR =tert. butyl:

D. R =R =tert. butyl: g

The coking panel rating gives an indication of the" formation of insoluble polymeric materials which cause piston deposits. The panels are read in arbitrary units from 0 corresponding to as new through 7 corresponding to complete coking. In general ratings from 0-3 are satisfactory.

We claimz- 1. A lubricant composition comprising a lubricant base and, as an antioxidant, at least one substituted 2-hydroxyphenylamine of formula R OH in which X represents an aromatic radical of formula sis-ting of the p-phenylene radical, the m-tolylene radical, the p-Xylylene radical, and the radicals of formulae:

PATRICK P. GARVIN, Primary Examiner W. J. SHINE, Assistant Examiner 

